1. Field of the Invention
The present invention relates to a device for positioning a retractable seat belt, and more particularly, to a device for automatically positioning a shoulder harness of a vehicle retractable seat belt for maximum fit and comfort of a vehicle occupant regardless of the body size of the occupant, and to a system utilizing the device to simply and automatically adjust the seat belt.
2. Description of the Related Art
A conventional three-point seat belt restraint system is comprised of a lap belt segment and a shoulder harness segment. One end of a length of seat belt webbing is affixed to a vehicle frame structure on one side of the passenger seat, either near or on the vehicle floor, by a first anchor mount. The other end is attached to a seat belt retractor which is mounted on or near the vehicle roof on the same side of the passenger seat as the first anchor mount. The seat belt is provided with an adjustable tongue plate adapted for locking engagement with a seat belt buckle which is anchored on the opposite side of the passenger seat as the first seat belt anchor mount and the retractor. The belt webbing between the first anchor mount and tongue plate crosses over the lap of the passenger, and is thus referred to as the "lap belt" segment of the seat belt. The belt webbing between the tongue plate and retractor comes from behind, over the shoulder, and falls diagonally across the upper torso of the vehicle occupant, and is thus referred to as the "shoulder harness" segment of the seat belt.
The comfort and effectiveness of a shoulder harness depends, in large part, on where the harness is positioned on the vehicle occupant's torso. However, a conventional seat belt system is designed to accommodate only one size passenger, this being an adult passenger of average height. A shoulder harness arrangement of such dimensions may not be comfortable when applied over a smaller passenger. If the shoulder harness dimensioned for an adult is worn by a smaller passenger and is not correctly positioned, the shoulder harness ceases to be a safety device and may even increase the risk of serious injury to the passenger during a vehicular collision. Further, considering human nature, if the harness is not comfortable there is a tendency for the passenger not to wear the seat belt in the manner in which it is designed to be worn (i.e., the shoulder harness may be moved behind the back), thus preventing the seat belt from properly performing its function as an upper torso restraining device. Accordingly, comfort is a very important design feature.
Despite the importance of correct positioning of the shoulder harness, most conventional seat belt restraint systems provided in vehicles today do not provide any way for automatically accommodating the shoulder harness to individuals of different sizes.
Various attempts have been made in the past to render conventional shoulder harnesses adjustable, but these attempts have proven to be less than optimal solutions to the problem. For example, U.S. Pat. No. 4,893,835 to Linden discloses a deflection device for shortening the length of the shoulder belt portion in order to position it across the chest of a smaller seat occupant such as a child. However, this device is only useful for seat belts having not only the lap belt segment and the shoulder harness segment, but also an additional vertical run of webbing along the door post below the upper anchor point of the shoulder belt segment anchoring point. Further, this system requires the seat belt to be manually adjusted each time the size of the vehicle occupant changes. Further yet, the device may interfere with the retraction mechanism. U.S. Pat. No. 4,796,919 to Linden likewise teaches a deflection device for shortening the length of the shoulder belt portion and disposing it across the chest of a smaller seat occupant such as a child. This device is not automatic, and can only be used in seat belt systems including a vertical run of seat belt webbing below the door post anchorage of the shoulder belt.
U.S. Pat. No. 4,799,737 to Greene teaches an auxiliary shoulder belt adjuster which will permit the shoulder belt of a conventional vehicular restraint system to be adjusted in accordance with the height requirements of a seated individual. The auxiliary adjusting device has a first, upper, attachment point for adjusting the seat belt for a conventional adult sized individual and a second, lower, attachment point for adjusting the belt for shorter individuals. However, due to the reliance on secondary anchoring points away from the main seat belt anchoring points, the device appears to reduce the load bearing capacity of the belt. Further, the device is not automatic, but must be adjusted each time the size of the passenger changes.
U.S. Pat. No. 5,255,940 to Kornblum et al. teaches an add-on device for repositioning the shoulder restraint belt to make it adjustable for the comfort and safety of the user. However, the device is liable to the same deficiencies as discussed above.
U.S. Pat. No. 5,340,198 to Murphy et al. also teaches a safety belt adjustment device for lowering the point at which the shoulder harness crosses the center of the passenger's chest. The device is not automatic and is liable to the deficiencies discussed above.
U.S. Pat. No. 5,074,589 discloses an automatic seat belt wherein the lap seat belt and shoulder seat belt are automatically set to restrain a seated person. A first end of each belt is slidable in a guide rail diagonally disposed on the inner surface of the door. Second ends of the belts are fixed on the inner side of the seat bottom and on the inner portion of the seat back respectively. When the first ends of the seat belts are in the highest position of the guide rail, the seated person is in a free state. When the first ends are slid and set in the lowest position, the seat belts restrain the person. The construction cost of such a system is prohibitive to the small manufacturer.
Due to the importance of shoulder harness fit, the Department of Transportation, National Highway Traffic Safety Administration (NHTSA) has investigated the problem and is proposing new requirements which will render the above-discussed positioning devices obsolete. NHTSA's research indicated that a significantly lower percentage of both non-adjustable and adjustable belts were within the comfort zone for the six-year-old dummy than for the adult dummies. As set forth in 49 CFR Part 571 [Docket No. 74-14; Notice 91]; RIN 2127-AE48; Federal Motor Vehicle Safety Standards; Occupant Crash Protection published Aug. 3, 1994, NHTSA found that some vehicle occupants who find their safety belts to be uncomfortable react to their discomfort either by wearing their safety belts incorrectly or by not wearing them at all. NHTSA considered that improving safety belt fit will encourage the correct use of safety belts usage rate, and thus proposes to amended Standard No. 208. Occupant Crash Protection, to require that Type 2 safety belts installed for adjustable seats in vehicles to either be integrated with the vehicle seat or be equipped with a means of adjustability to improve the fit and increase the comfort of the belt for a variety of different sized occupants by 1997.
Although the need was obvious, an economical, simple design which could satisfy the requirements was not so obvious. Proposed designs included the following:
An adjustable upper anchorage device (AUA) which provides a means of adjusting the upper anchorage of the shoulder belt and which has at least two distinct positions separated by at least 5 centimeters, measured linearly. However, such a device adds mechanical complexity and cost.
A floor-mounted inboard adjustable anchorage which is similar to the AUA but is mounted on the floor on the inboard side of the seat. This device must have at least two distinct adjustment positions for moving the device or webbing at least 5 centimeters, measured linearly. Again, the mechanical complexity increases cost, and the moveability of the floor mount reduces load bearing capacity.
An integrated safety belt assembly which is anchored completely to the seat structure. For a moveable seat, the anchorages must be located on a part of the seat above the seat adjuster. Such a design increases cost.
A "semi-integrated" safety belt assembly which has the upper anchorage and the retractor for the upper torso portion of the Type 2 belt mounted to the moving portion of the seat structure. Other similar "semi-integrated" designs include: lower anchorages for the upper torso belt mounted on the movable portion of the seat; shoulder belt guides; and through-the-seat routing of the safety belt webbing. The movement of the device, measured linearly, must be at least 5 centimeters. Again, design and construction costs would increase.
Sling-mounted D-rings comprising an upper shoulder belt anchorage D-ring, used to relocate the D-ring closer to the occupant. The sling usually rotates freely around the anchorage bolt to permit D-ring movement. Sling-mounted D-rings designed in this manner do not have two distinct adjustment positions and would not comply with the adjustability requirement. NHTSA indicated that it does not believe that a sling-mounted D-ring which does not have district adjustment positions should be allowed as the position of such a device would change due to vehicle vibration or occupant movement, resulting in reduced comfort for the occupant.
An international seat retractor is a safety belt retractor that would permit the introduction of slack in the upper torso portion of the safety belt. Such a device could not be used to comply with the new NHTSA requirement.
An example of the type of design that would meet the requirement of S7.1.2.1 is a Volvo design in which the shoulder belt webbing is fed through a slot in the pillar at different angles and in different locations as increasing amounts of webbing are spooled off the conical spool of the retractor. This design is mechanically complicated and expensive. Increased mechanical complexity introduces the possibility of mechanical failure.
Porsche described a system which adjusts the seat height relative to a fixed D-ring to be used to comply with the adjustability requirement. NHTSA is not amending the language to allow the use of this system as a means of compliance, since occupants use seat adjustability primarily as a means of reaching controls and increasing visibility out of the vehicle.
The above relates mainly to adjustable front seats. NHTSA received comments from manufacturers indicating that there were greater design problems with designing rear seats to comply with the adjustability requirement, and that compliance was costlier for these seats with little benefits.
Thus, it becomes apparent that there exists a real need for a simple and economical device for automatically adjusting a shoulder harness of a vehicle retractable seat belt for maximum comfort of a vehicle occupant regardless of the body size of the occupant, and to a system utilizing the device to simply and automatically adjust the shoulder harness.
There is a need for a device and system which can automatically adjust a shoulder harness for an occupant of a fixed rear seat as well as for a moveable front seat.
There is also a need for a device and system which utilizes lighter weight components, is relatively simple in design and construction, inexpensive to fabricate and assemble, and yet is durable and highly reliable.